Tent and Camera 65 



focus and expose as nearly simultaneously as possible. To 

 meet these requirements the twin -lens and reflecting cameras, 

 both of which are old inventions, 1 have in recent years been 

 placed on the market in improved and serviceable forms. 



The "twin-lens" consists of two cameras, set one above the 

 other, the bellows of which move as one. The lower takes the 

 picture, while the upper gives the image which is reflected on 

 a glass plate set in the top of the box. Besides being expensive 

 and heavy, the trade sizes of these cameras are apt to be of too 

 short focus to be of much service to the animal photographer. 



The reflecting camera does the work of the two lenses with 

 a single lens and bellows, and in the recent designs 2 is provided 

 with a focal plane shutter, which is the best for exposures 

 quicker than the T J )(i second mark of ordinary shutters. Like 

 the upper half of the "twin-lens," it has a movable mirror, set 

 at an angle of 45, which casts the image made by the lens on a 

 plate of ground glass set in the top of the box and shielded by 

 an adjustable hood. The mirror is so placed between the plate 

 and lens that the distance from lens to sensitive plate equals 

 the distance traversed by light in passing from lens to mirror 

 and ground glass. When the object is focused, a lever is 

 pressed which raises the mirror and automatically releases the 

 shutter. One must expect to find the image on the ground glass 

 somewhat dimmer than when no interposing mirror is used. To 

 be most serviceable this camera should have a long bellows. 



The Lens. In animal photography, short- and long-focus and 

 telephoto lenses are available. My own experience has been 

 mainly limited to the following: Zeiss Anastigmat, Series ii a, 

 6inch., speed -; Convertible Anastigmat, Series vii a, combined 



1 The principle of the reflecting camera was applied as early as 1860, 

 and various forms of the reflex type were devised during the next thirty 

 years. In 1891 Dr. Kriigener of Frankfort brought out his "Normal 

 Reflex-Camera," in which the construction, though somewhat compli- 

 cated, was much improved. The principles are essentially the same in 

 the later designs : see Ausfuhrliches Handbuch der Photographic, by Josef 

 Maria Eder, Halle, 1891. 



2 The improved Graflex camera, manufactured by The Folmer and 

 Schwing Mfg. Co., New York, is excellent in design and workmanship. 



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